TLR4-mediated pyroptosis in human hepatoma-derived HuH-7 cells induced by a branched-chain polyunsaturated fatty acid, geranylgeranoic acid

BaP/BPDE exposure causes human trophoblast cell dysfunctions and induces miscarriage by up-regulating lnc-HZ06-regulated IL1B

Exposure to environmental BaP or its metabolite BPDE causes trophoblast cell dysfunctions to induce miscarriage (abnormal early embryo loss), which might be generally regulated by lncRNAs. IL1B, a critical inflammatory cytokine, is closely associated with adverse pregnancy outcomes. However, whether IL1B might cause dysfunctions of BaP/BPDE-exposed trophoblast cells to induce miscarriage, as well as its specific epigenetic regulatory mechanisms, is completely unexplored. In this study, we find that BPDE-DNA adducts, trophoblast cell dysfunctions, and miscarriage are closely associated. Moreover, we also identify a novel lnc-HZ06 and IL1B, both of which are highly expressed in BPDE-exposed trophoblast cells, in villous tissues of recurrent miscarriage patients, and in placental tissues of BaP-exposed mice with miscarriage. Both lnc-HZ06 and IL1B suppress trophoblast cell migration/invasion and increase apoptosis. In mechanism, lnc-HZ06 promotes STAT4-mediated IL1B mRNA transcription, enhances IL1B mRNA stability by promoting the formation of METTL3/HuR/IL1B mRNA ternary complex, and finally up-regulates IL1B expression levels. BPDE exposure promotes TBP-mediated lnc-HZ06 transcription, and thus up-regulates IL1B levels. Knockdown of either murine lnc-hz06 (which down-regulates Il1b levels) or murine Il1b could alleviate miscarriage in BaP-exposed mice. Collectively, this study not only discovers novel biological mechanisms and pathogenesis of unexplained miscarriage but also provides novel potential targets for treatment against BaP/BPDE-induced miscarriage.

Induction of Hepatoma Cell Pyroptosis by Endogenous Lipid Geranylgeranoic Acid-A Comparison with Palmitic Acid and Retinoic Acid

Research on retinoid-based cancer prevention, spurred by the effects of vitamin A deficiency on gastric cancer and subsequent clinical studies on digestive tract cancer, unveils novel avenues for chemoprevention. Acyclic retinoids like 4,5-didehydrogeranylgeranoic acid (4,5-didehydroGGA) have emerged as potent agents against hepatocellular carcinoma (HCC), distinct from natural retinoids such as all-trans retinoic acid (ATRA). Mechanistic studies reveal GGA's unique induction of pyroptosis, a rapid cell death pathway, in HCC cells. GGA triggers mitochondrial superoxide hyperproduction and ER stress responses through Toll-like receptor 4 (TLR4) signaling and modulates autophagy, ultimately activating pyroptotic cell death in HCC cells. Unlike ATRA-induced apoptosis, GGA and palmitic acid (PA) induce pyroptosis, underscoring their distinct mechanisms. While all three fatty acids evoke mitochondrial dysfunction and ER stress responses, GGA and PA inhibit autophagy, leading to incomplete autophagic responses and pyroptosis, whereas ATRA promotes autophagic flux. In vivo experiments demonstrate GGA's potential as an anti-oncometabolite, inducing cell death selectively in tumor cells and thus suppressing liver cancer development. This review provides a comprehensive overview of the molecular mechanisms underlying GGA's anti-HCC effects and underscores its promising role in cancer prevention, highlighting its importance in HCC prevention.

Carvedilol induces pyroptosis through NLRP3-caspase1-ASC inflammasome by nuclear migration of NF-κB in prostate cancer models

BACKGROUND

Pyroptosis is an inflammatory type of programmed cell death, and could overcome the drug-resistance induced by anti-apoptotic effect of cancers. Carvedilol (CVL), a β-adrenergic receptors antagonist, has shown anti-inflammatory response and anti-cancer effect. The aim of this study is to investigate whether pyroptosis can be activated by CVL in prostate cancer (PCa).

METHODS AND RESULTS

Datasets were used to analyze the expressions of pyroptosis-related proteins. Intracellular morphological change, cell viability, LDH and Il-1β release by cells,, and Hoechst/PI staining were used to detect the occurrence of pyroptosis. Realtime-PCR, western blot, immunofluorescence, and immunohistochemistry (IHC) were used to investigate the expressions of pyroptosis-related proteins. Datasets analyze showed the expressions of NLRP3, Caspase 1, ASC and GSDMD were all decreased in PCa comparing with normal tissues, but without prognostic significance. CVL treatment weakened the viabilities of PCa cells. Cell morphology changing, cytoplasmic vacuole formation, membrane integrity loss, LDH and IL-1β release and PI positive cells increasing were observed. NLRP3, Caspase 1, ASC, GSDMD and N-GSDMD expressions were elevated after CVL treatment, accompanied by a tendency of NF-κB transferring into nucleus. In vivo, CVL inhibited the growth of subcutaneous transplanted tumor. IHC showed CVL increased the expressions of NLRP3, ASC, and GSDMD, and decreased the expression of Ki-67 in transplanted tumor tissues.

CONCLUSION

This study demonstrated that CVL could induce pyroptosis in PCa cells through NLRP3-caspase1-ASC inflammasome by promoting nuclear translocation of NF-κB, which would lay a foundation for the application of adrenergic receptor antagonist in PCa.

Ferroptosis, Necroptosis, and Pyroptosis in Gastrointestinal Cancers: The Chief Culprits of Tumor Progression and Drug Resistance

In recent years, the incidence of gastrointestinal cancers is increasing, particularly in the younger population. Effective treatment is crucial for improving patients' survival outcomes. Programmed cell death, regulated by various genes, plays a fundamental role in the growth and development of organisms. It is also critical for maintaining tissue and organ homeostasis and takes part in multiple pathological processes. In addition to apoptosis, there are other types of programmed cell death, such as ferroptosis, necroptosis, and pyroptosis, which can induce severe inflammatory responses. Notably, besides apoptosis, ferroptosis, necroptosis, and pyroptosis also contribute to the occurrence and development of gastrointestinal cancers. This review aims to provide a comprehensive summary on the biological roles and molecular mechanisms of ferroptosis, necroptosis, and pyroptosis, as well as their regulators in gastrointestinal cancers and hope to open up new paths for tumor targeted therapy in the near future.

Geranylgeranoic acid, a bioactive and endogenous fatty acid in mammals: a review

Geranylgeranoic acid (GGA) was first reported in 1983 as one of the mevalonic acid (MVA) metabolites, but its biological significance was not studied for a long time. Our research on the antitumor effects of retinoids led us to GGA, one of the acyclic retinoids that induce cell death in human hepatoma-derived cell lines. We were able to demonstrate the presence of endogenous GGA in various tissues of male rats, including the liver, testis, and cerebrum, by LC-MS/MS. Furthermore, the biosynthesis of GGA from MVA in mammals including humans was confirmed by isotopomer spectral analysis using ¹³C-labeled mevalonolactone and cultured hepatoma cells, and the involvement of hepatic monoamine oxidase B (MAOB) in the biosynthesis of GGA was also demonstrated. The biological activity of GGA was analyzed from the retinoid (differentiation induction) and non-retinoid (cell death induction) aspects, and in particular, the non-retinoid mechanism by which GGA induces cell death in hepatoma cells was found to involve pyroptosis via ER-stress responses initiated by TLR4 signaling. In addition to these effects of GGA, we also describe the in vivo effects of GGA on reproduction. In this review, based mainly on our published papers, we have shown that hepatic MAOB is involved in the biosynthesis of GGA and that GGA induces cell death in human hepatoma-derived cell lines by non-canonical pyroptosis, one of the mechanisms of sterile inflammatory cell death.

The Role of the NLRP3 Inflammasome in HCC Carcinogenesis and Treatment: Harnessing Innate Immunity

Simple Summary

The Hepatocellular Carcinoma (HCC) remains a major concern for the public health. The pandemic of metabolic syndrome in the Western societies and the considerable amounts of viral hepatitis in the underdeveloped countries keep fueling s the development of HCC. The hepatotropic viruses evade the NLRP3 inflammasome in order to sustain the chronicity of infection leading to cirrhosis while in the established tumors the activation of NLRP3 promotes several pro-tumorigenic effects. That leads to substantial economic burden for the societies and alternative therapeutic targets should be investigated. Reviewing past and more recent literature it can be deduced that the NLRP3 inflammasome could be an ideal therapeutic effects and it should be studied in more depth.

Abstract

The HCC constitutes one of the most frequent cancers, with a non-decreasing trend in disease mortality despite advances in systemic therapy and surgery. This trend is fueled by the rise of an obesity wave which is prominent the Western populations and has reshaped the etiologic landscape of HCC. Interest in the nucleotide-binding domain leucine-rich repeat containing (NLR) family member NLRP3 has recently been revived since it would appear that, by generating inflammasomes, it participates in several physiologic processes and its dysfunction leads to disease. The NLRP3 inflammasome has been studied in depth, and its influence in HCC pathogenesis has been extensively documented during the past quinquennial. Since inflammation comprises a major regulator of carcinogenesis, it is of paramount importance an attempt to evaluate the contribution of the NLRP3 inflammasome to the generation and management of HCC. The aim of this review was to examine the literature in order to determine the impact of the NLRP3 inflammasome on, and present a hypothesis about its input in, HCC.

Dietary Fatty Acid Regulation of the NLRP3 Inflammasome via the TLR4/NF-κB Signaling Pathway Affects Chondrocyte Pyroptosis

Dietary fatty acid (FA) content and type have different effects on obesity-associated osteoarthritis (OA), but the mechanisms underlying these differences are not fully understood. Inflammation activated by toll-like receptor 4 (TLR4)/nuclear factor- (NF-) κB signaling and pyroptosis induced by the NLRP3/caspase-1/gasdermin D (GSDMD) signaling pathway play important roles in OA development. Our aim in this study was to observe the effects of dietary FAs on the articular cartilage of obese post-traumatic OA model mice and on chondrocytes stimulated by lipopolysaccharide (LPS) and to determine whether the underlying mechanisms involve TLR4/NF-κB and NLRP3/caspase-1/GSDMD signaling pathways. Mice were fed high-fat diets rich in various FAs and underwent surgical destabilization of the medial meniscus to establish the obesity-related post-traumatic OA model. LPS-induced SW1353 chondrosarcoma cells were used to mimic OA status in vitro, and TLR4 inhibitors or TLR4 overexpressing lentivirus was administered. Analysis using weight-matched mice and multiple regression models revealed that OA was associated with dietary FA content and serum inflammatory factor levels, but not body weight. Diets rich in n-3 polyunsaturated fatty acids (PUFAs) attenuated OA and inhibited the TLR4/NF-κB and NLRP3/caspase-1/GSDMD signaling pathways, whereas diets rich in saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), or n-6 PUFAs increased OA severity and activated these pathways. In vitro results for SFAs, n-6 PUFAs, and n-3 PUFAs were consistent with the animal experiments. However, those for MUFAs were not. FA effects on the NLRP3/caspase-1/GSDMD pathway were associated with the inhibition or activation of the TLR4 signaling pathway. In conclusion, diets rich in SFAs or n-6 PUFAs can exacerbate obesity-associated OA, whereas those rich in n-3 PUFAs have protective effects against this disease, due to their respective pro-/anti-inflammatory and pyroptotic effects. Further research on dietary FA supplements as a potential therapeutic approach for OA is needed.

A Novel Pyroptosis-Related Prognostic Signature for Risk Stratification and Clinical Prognosis in Clear Cell Renal Cell Carcinoma

Emerging research has substantiated that pyroptosis-related biomarkers were mightily related to the clinical outcome of patients with clear cell renal cell carcinoma (ccRCC). However, a single-gene biomarker's moderate predictive power is insufficient, and more accurate prognostic models are urgently needed. We conducted this investigation in order to develop a robust pyroptosis-related gene signature for use in risk stratification and survival prognosis in colorectal cancer. We downloaded transcriptomic data and survival information of ccRCC patients from TCGA. Bioinformatic methods were used to generate a pyroptosis-related gene signature based on data from TCGA training cohort. ROC curve, uni- and multivariate regression analyses were used for the prognostic assays. What is more, we explored the relationship between model-based risk score and the tumor microenvironment. Herein, 11 pyroptosis-related hub genes (CASP9, TUBB6, NFKB1, BNIP3, CAPN1, CD14, PRDM1, BST2, SDHB, TFAM, and GSDMB) were determined as risk signature for risk stratification and prognosis prediction for ccRCC. Kaplan-Meier curves, ROC curves, and risk plots were employed to analyze and verify its performance in all groups. Multivariate assays exhibited that risk score could be an independent prognostic factor for patients' OS. ESTIMATE algorithm showed a higher immune score in the group of high-risk. Overall, a novel pyroptosis-related gene signature generated can be employed for prognosis prediction of ccRCC patients. This may assist in individual treatment of clinical decision-making.

Hepatic CYP3A4 Enzyme Compensatively Maintains Endogenous Geranylgeranoic Acid Levels in MAOB-Knockout Human Hepatoma Cells

Geranylgeranoic acid (GGA), developed as a preventive agent against second primary hepatoma, has been reported to be biosynthesized via the mevalonate pathway in human hepatoma-derived cells. Recently, we found that monoamine oxidase B (MAOB) catalyzed the oxidation of geranylgeraniol (GGOH) to produce geranylgeranial (GGal), a direct precursor of endogenous GGA in hepatoma cells, using tranylcypromine, an inhibitor of MAOs, and knockdown by MAOB siRNA. However, endogenous GGA level was unexpectedly unchanged in MAOB-knockout (KO) cells established using the CRISPR-Cas9 system, suggesting that some other latent metabolic pathways maintain endogenous GGA levels in the MAOB-KO cells. Here, we investigated the putative latent enzymes that oxidize GGOH in Hep3B/MAOB-KO cells. First, the broad-specific cytochrome P450 enzyme inhibitors decreased the amount of endogenous GGA in Hep3B/MAOB-KO cells in a dose-dependent manner. Second, among the eight members of cytochrome P450 superfamily that have been suggested to be involved in the oxidation of isoprenols and/or retinol in previous studies, only the CYP3A4 gene significantly upregulated its cellular mRNA level in Hep3B/MAOB-KO cells. Third, a commercially available recombinant human CYP3A4 enzyme was able to oxidize GGOH to GGal, and fourth, the knockdown of CYP3A4 by siRNA significantly reduced the amount of endogenous GGA in Hep3B/MAOB-KO cells. These results indicate that CYP3A4 can act as an alternative oxidase for GGOH when hepatic MAOB is deleted in the human hepatoma-derived cell line Hep3B, and that endogenous GGA levels are maintained by a multitude of enzymes.

Novel Risk Classification Based on Pyroptosis-Related Genes Defines Immune Microenvironment and Pharmaceutical Landscape for Hepatocellular Carcinoma

Growing evidence has indicated that pyroptosis functions in the development of cancer. Nonetheless, specific roles of pyroptosis-related genes in tumor progression, immune response, prognosis, and immunotherapy have not been thoroughly elucidated. After a comprehensive evaluation of pyroptosis genes, unsupervised clustering was performed to generate three distinct clusters from hepatocellular carcinoma (HCC) samples. Three distinct pyroptosis-related molecular subtypes comprising three gene clusters that had differential prognostic effects on patient survival were then identified. Immune characteristics analyses revealed diversified immune cell infiltration among the subtypes. Two clusters served as immune-hot phenotypes associated with significantly poorer survival compared to a remaining third immune-cold cluster. Among these, the immune-hot clusters were characterized by abundant adaptive immune cell infiltration, active CD4+ and CD8+ T cells, high total leukocyte counts and tumor growth status, and lower Th17 cell and M2 macrophage densities. Then, risk scores indicated that low-risk patients were more sensitive to anti-tumor therapy. Subsequently, we found a significant correlation between pyroptosis and prognosis in HCC and that pyroptosis genes drive the heterogeneity of the tumor microenvironment. The risk scoring system, based on pyroptosis-related differentially expressed genes, was established to evaluate the individual outcomes and contribute to new insights into the molecular characterization of pyroptosis-related subtypes.

A rapid increase in lysophospholipids after geranylgeranoic acid treatment in human hepatoma-derived HuH-7 cells revealed by metabolomics analysis

Geranylgeranoic acid (GGA) was developed as a preventative agent against second primary hepatoma, and was reported to induce cell death in human hepatoma cells via Toll-like receptor 4 (TLR4)-mediated pyroptosis. We recently reported that GGA is enzymatically biosynthesized from mevalonic acid in human hepatoma-derived HuH-7 cells and that endogenous GGA is found in most rat organs including the liver. An unbiased metabolomics analysis of ice-cold 50% acetonitrile extracts from control and GGA-treated cells was performed in this study to characterize the intracellular metabolic changes in GGA-induced pyroptosis and to analyze their relationship with the mechanism of GGA-induced cell death. The total positive ion chromatograms of the cellular extracts in ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry were apparently unchanged after GGA treatment, but an orthogonal partial least squares-discriminant analysis score plot clearly discriminated the intracellular metabolite profiles of GGA-treated cells from that of control cells. S-plot analysis revealed 15 potential biomarkers up-regulated by 24-h GGA treatment according to their variable importance in the projection value of more than 1, and the subsequent metabolomics analysis identified nine of these metabolites as a group of lysophospholipids containing lysophosphatidylcholine with C16:0, C20:4, or C20:3 fatty acids. The possible roles of these lysophospholipids in GGA-induced pyroptosis are discussed.

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Metabolomics analysis was performed on geranylgeranoic acid (GGA)-treated cells.

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Total positive ion chromatograms were apparently similar after GGA treatment.

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The OPLS-DA score plot distinguished the GGA-treated cells from control cells.

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The S-plot analysis revealed GGA-induced upregulation of lysophospholipids.

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The possible roles of lysophospholipids in GGA-induced pyroptosis are discussed.

Age-Dependent Decrease in Hepatic Geranylgeranoic Acid Content in C3H/HeN Mice and Its Oral Supplementation Prevents Spontaneous Hepatoma

Geranylgeranoic acid (GGA) has been developed as a preventive agent against second primary hepatoma. Recently, GGA was reported to induce cell death in human hepatoma cells via TLR4-mediated pyroptosis. We have reported that GGA is enzymatically biosynthesized from mevalonic acid in human hepatoma-derived cells and that endogenous GGA is found in most organs of rats. In addition, we found that upregulation of endogenous GGA levels by zaragozic acid A (ZAA) induced cell death in human hepatoma-derived cells. Therefore, we investigated the age-related changes in hepatic GGA and the possibility of suppressing hepatocarcinogenesis by GGA supplementation using male C3H/HeN mice that spontaneously develop hepatoma. We measured endogenous GGA and mRNA of monoamine oxidase (BMAOB), a key enzyme of GGA biosynthesis, in the liver of male C3H/HeN mice aged 6–93 weeks. We also tried suppressing spontaneous hepatocarcinogenesis by a single administration of GGA to C3H/HeN mice. Hepatic GGA content and Maob mRNA expression level age-dependently decreased in male C3H/HeN mice; some of which produced spontaneous hepatoma in 2 years. A single oral administration of GGA at 11 months of age significantly prevented hepatoma in terms of the number and weight of tumors per mouse at 24 months. Oral supplementation with GGA or geranylgeraniol significantly increased endogenous hepatic GGA contents dose-dependently; and ZAA dramatically upregulated hepatic GGA. In this study; we found an age-dependent decrease in hepatic endogenous GGA in male C3H/HeN mice and efficient prevention of spontaneous hepatoma by a single administration of GGA at 11 months of age.

Pyroptosis, metabolism, and tumor immune microenvironment

In response to a wide range of stimulations, host cells activate pyroptosis, a kind of inflammatory cell death which is provoked by the cytosolic sensing of danger signals and pathogen infection. In manipulating the cleavage of gasdermins (GSDMs), researchers have found that GSDM proteins serve as the real executors and the deterministic players in fate decisions of pyroptotic cells. Whether inflammatory characteristics induced by pyroptosis could cause damage the host or improve immune activity is largely dependent on the context, timing, and response degree. Here, we systematically review current points involved in regulatory mechanisms and the multidimensional roles of pyroptosis in several metabolic diseases and the tumor microenvironment. Targeting pyroptosis may reveal potential therapeutic avenues.

Cucurbitacin B inhibits non-small cell lung cancer in vivo and in vitro by triggering TLR4/NLRP3/GSDMD-dependent pyroptosis

Pyroptosis, a type of programmed cell death (PCD), is characterized by cell swelling with bubbles, and the release of inflammatory cell cytokines. Cucurbitacin B (CuB), extracted from muskmelon pedicel, is a natural bioactive product that could effectively exert anti-tumor activities in lung cancer. However, the exact molecular mechanisms and the direct targets of CuB in non-small cell lung cancer (NSCLC) remain to be discovered. Here, we firstly found that CuB exerted an anti-tumor effect via pyroptosis in NSCLC cells and NSCLC mice models. Next, based on the molecular docking and cellular thermal shift assay (CETSA), we identified that CuB directly bound to Toll-like receptor 4 (TLR4) to activate the NLRP3 inflammasome, which further caused the separation of N- and C-terminals of Gasdermin D (GSDMD) to execute pyroptosis. Moreover, CuB enhanced the mitochondrial reactive oxygen species (ROS), mitochondrial membrane protein Tom20 accumulation, and cytosolic calcium (Ca2+) release, leading to pyroptosis in NSCLC cells. Silencing of TLR4 inhibited CuB-induced pyroptosis and decreased the level of ROS and Ca2+ in A549 cells. In vivo study showed that CuB treatment suppressed lung tumor growth in mice via pyroptosis without dose-dependent manner, and CuB at 0.75 mg/kg had a better anti-tumor effect compared to the Gefitinib group. Taken together, our findings revealed the mechanisms and targets of CuB triggering pyroptosis in NSCLC, thus supporting the notion of developing CuB as a promising therapeutic agent for NSCLC.